Diagnostic function for an internal combustion engine

Abstract

A diagnostic function for an internal-combustion engine whose power is set by way of a power-determining signal that is determined from a first signal from a determination device, and a second signal determined by a torque controller, based on engine torque. A selection device sets either the determination device or the torque controller to be dominant for the power determining signal. When the values of the engine torque are not plausible, an error mode is set. With the setting of the error mode, the dominance is retained when the determination device is dominant. When the torque controller is dominant, a change of the dominance takes place.

1. A diagnostic process for an internal-combustion engine whose power is controlled by a power-determining signal, said internal combustion engine including a determination device that determines a first signal from the engine torque, based on a desired value definition, a torque controller that determines a second signal and a selection device that sets either the determination device or the torque controller to be dominant for the power-determining signal; said process comprising:
 setting an error mode when values of engine torque are not plausible;  
 upon setting of the error mode, if the determination device is dominant, retaining the dominance of the determination device; and  
 upon setting of the error mode, if the torque controller is dominant, implementing a change of the dominance.  
 
   
   
     2. The diagnostic process according to  claim 1 , wherein the change of dominance is implemented from the torque controller to the determination device according to a transition function by means of a diagnostic block. 
   
   
     3. The diagnostic process according to  claim 2 , wherein according to the transition function, the engine torque is controlled from a last plausible value to zero. 
   
   
     4. The diagnostic process according to  claim 2 , wherein according to the transition function, the second signal is controlled from a last plausible value to a higher value. 
   
   
     5. The diagnostic process according to  claim 3 , wherein the transition function is implemented as one of a mathematical function and a filtering function. 
   
   
     6. The diagnostic process according to  claim 4 , wherein the transition function is implemented as one of a mathematical function and a filtering function. 
   
   
     7. The diagnostic process according to  claim 1 , wherein when the error mode is set, a limit value curve providing a maximum permissible first signal is adapted. 
   
   
     8. The diagnostic function according to  claim 7 , wherein the limit value curve is adapted toward smaller values of the first signal. 
   
   
     9. The diagnostic process according to  claim 1 , wherein the error mode is set back when plausible values of engine torque moment are detected again, after a time step has expired.